The present invention generally relates to rivet guns, and specifically relates to rivet retention systems for use with rivet guns.
Rivet guns, such as hydraulic rivet guns, have a head portion which engages a powered body portion. In the case of a hydraulic rivet gun, a C-frame assembly 10 such as is shown in FIG. 1 may engage a hydraulic-powered handle (not specifically shown in FIG. 1). The C-frame assembly 10 includes a C-frame body portion 12 which engages the handle, and is secured to the handle using screws 14.
A threaded bolt 16 is provided, and the threaded bolt 16 includes a head portion 18 and a threaded shaft portion 20. The threaded shaft portion 20 extends through a throughbore 22 which is provided in a back bushing 24 and threadably engages in a front bushing 26. The back bushing 24 and front bushing 26 are disposed in a chamber 28 which is provided in the C-frame 12. A compression spring 30 is also disposed in the chamber 28, generally between the body portion 12 and the handle (not specifically shown in FIG. 1). As such, the rivet gun is hydraulically powered (viz-a-viz the handle) and is spring return (viz-a-viz spring 30).
The C-frame 10 includes spacing 32 for receiving a workpiece. Proximate the spacing 32 is an opening 34 which is in communication with the chamber 28 in which the front bushing 26 is disposed. An end 36 of the front bushing 26 includes a bore 38 for receiving a back end of a punch (not specifically shown in FIG. 1). Specifically, the back end of the punch extends into the opening 34 in the C-frame 12 and extends into the bore 38 in the end 36 of the front bushing 26. A set screw 40 secures the back end of the punch and holds the punch in place relative to the front bushing 26. Proximate the spacing 32 in the C-frame 12 is another opening (not visible in FIG. 1) for receiving an end of a die (not specifically shown in FIG. 1). A set screw 42 is provided to secure the end of the die and hold the die in place relative to the C-frame 12.
In use, a self-piercing rivet is placed inside the punch, and a workpiece is positioned in the spacing 32 provided in the C-frame 12. Then, the handle of the rivet gun is actuated, causing the punch to move toward the die, causing the rivet to set in the workpiece. After the rivet sets, the punch returns to its starting position via the spring force exerted by spring 30.
A problem which exists with regard to rivet guns, such as a hydraulic rivet gun which uses a C-frame as shown in FIG. 1, is the positioning of the rivet in the punch before the gun is actuated. If the rivet is not properly aligned before the rivet gun is actuated, the rivet may not set right during actuation of the rivet gun. To assist in the aligning of rivets, a retaining member (not specifically shown in FIG. 1), such as a urethane ring, may be provided on an end of the punch. However, such retaining members (especially their inside diameters) tend to get worn, thereby losing their effectiveness for precisely positioning rivets.
Furthermore, some rivet guns, such as those rivet guns which us a set of jaws to hold a rivet for broaching, are not practical for some applications. For example, some applications, such as roofing applications, provide that a workpiece is multiple-layered, having glue disposed between at least two of the layers. During riveting, glue may squirt onto the rivet gun, thereby diminishing the effectiveness of the gun during subsequent operation.